The present invention relates to medical instruments utilized in securing marrow tissue samples from bone structures.
A biopsy medical instrument is an instrument which is designed to take samples of tissue. Typically, a biopsy device that is utilized to obtain samples from the bone consists of a hollow cannula that is surrounding a stylet. The stylet includes a sharp distal tip which extends outwardly from the cannula when the stylet is secured inside the cannula. The combined cannula and stylet is used to penetrate through the outer layer of the bone, called the cortex, which is considerably harder than the trasecular bone layer and the tissue within the bone that is sampled, referred to as the marrow. Once the stylet and cannula have penetrated the cortex, the stylet is removed and the cannula is extended further into the medular cavity, thereby capturing marrow tissue for a sample.
The architecture of the tissue sample that is removed by the biopsy device is critical in several respects. Initially, the size of the sample is important, with larger tissue sample sizes representing better samples for subsequent testing to be performed on the tissue. However, the larger the cannula and stylet that are inserted into the bone, the more pain is generated at the site of the penetration for the patient. In addition, it is important that the sample be taken without damaging the marrow tissue. However, in removing the tissue sample the tissue must be excised from the remaining tissue. This removal can result in compromising the tissue sample by damaging the tissue sample.
Several approaches have been taken to secure large, undamaged tissue samples using bone marrow biopsy devices. However, each of these approaches has significant drawbacks which limit commercial and clinical usefulness. For example, one such approach utilizes suction provided at the proximal end of the cannula. The suction is designed to pull the tissue sample into the cannula and retain the tissue sample inside the cannula. While in theory such suction would help secure larger tissue samples, in practice exposure to such suction forces results in damage to the marrow tissue when the sample is removed from the patient.
Another approach utilizes a snare in the form of a coil at the distal end of the cannula. When rotated, the coil decreases in diameter to secure the biopsy tissue sample in the cannula. While again in theory such a device would help secure larger tissue samples, in practice it subjects the tissue sample to compression forces which causes damage to the sample.
Other approaches include the use of inwardly projecting members such as scallops within the cannula. The theory behind such devices is that when the tissue sample is inserted into the cannula, the inward direction of the scallops allows the tissue sample to slide over such projecting members but when the tissue sample is removed from the patient the projecting members latch onto the tissue sample to secure the tissue sample in the cannula. Again, however, this theory fails in practice as it causes trauma to the tissue when the tissue sample is removed from the patient.
Other approaches include providing apertures on the side of the cannula which, in theory, allow tissue to expand into such apertures to help secure the tissue sample in the cannula. Likewise, one approach utilizes a screw member in the cannula which is designed to urge the tissue inwardly and retain the tissue sample in of the cannula. Once again, providing a cavity for the tissue sample that is not smooth results in damage to the tissue when the tissue sample is removed from the patient.
Yet another approach at securing the biopsy sample within the cannula involves the use of a pair of coaxial cannulas. One of the two cannulas includes a curved section that acts as a cam to compress the inner cannula around the tissue sample when the inner cannula is withdrawn from the outer cannula. Once again, in theory this would help to secure the tissue within the cannula, but in practice it subjects the tissue sample to such compression forces that damage to the sample is caused. In addition, the use of dual cannulas acts to either decrease the size of the tissue sample or to increase the size of the biopsy device causing increased pain to the patient. A similar approach utilizes an additional coaxial hollow cannula designed to sheer or cut-off the tissue when the two cannulas are rotated relative to each other. However, because such devices require additional hardware in the cannula, either the size of the tissue sample is decreased or the size of the biopsy device is increased.
What would be desirable is a bone marrow biopsy device that is able to secure a large tissue sample while avoiding increasing the size of the biopsy device thereby minimizing the pain experienced by the patient during such procedure. Such a device would also avoid subjecting the tissue sample to undue forces, whether such forces be compression, suction, etc., to remove the tissue sample without causing undue damage to the tissue following removal of the sample from the patient.
The present invention is able to secure a large tissue sample while avoiding increasing the size of the biopsy device thereby minimizing the pain experienced by the patient during such procedure. The present invention further avoids subjecting the tissue sample to undue forces, whether such forces be compression, suction, etc., thus reducing damage to the tissue following removal of the sample from the patient.
The present invention provides a bone marrow biopsy device that includes a handle, an outer cannula, a stylet, and an inner member. The outer cannula is secured in the handle. The outer cannula defines a distal tip that is tapered to provide a distal cutting edge. The stylet is designed to be inserted in the outer cannula. The stylet defines a sharp distal tip. The inner member is designed to be inserted in the outer cannula. The inner member defines a cutting finger.
Thus, there is disclosed a bone marrow biopsy device comprising a handle; an outer cannula secured in the handle, the outer cannula defining a distal tip that provides a distal cutting edge; a stylet designed to be inserted in the outer cannula, the stylet defining a sharp distal tip; and an inner member designed to be inserted in the outer cannula, the inner member defining a cutting finger.
Thus, there is further disclosed a member for use with a bone marrow biopsy device comprising a proximal end formed with a hub that secures the member; and a distal end that defines a cutting finger.
There is further disclosed a kit for use in obtaining a bone marrow biopsy comprising a handle having an outer cannula secured therein, the outer cannula defining a distal tip that provides a distal cutting edge; a stylet designed to be inserted in the outer cannula, the stylet defining a sharp distal tip; and an inner member designed to be inserted in the outer cannula, the inner member defining a cutting finger.
There is disclosed a method for sampling bone marrow tissue comprising: inserting a stylet into an outer cannula; penetrating the bone cortex with the stylet and the outer cannula; removing the stylet; further inserting the outer cannula into a medular cavity, thereby trapping bone marrow tissue within the outer cannula; extending an inner member into the outer cannula, the inner cannula defining a cutting finger; rotating the inner member to shear off the specimen with the cutting finger; and removing the specimen from the patient.